1. Technical Field
This invention relates generally to internal combustion engines, and more particularly to cylinder liners for diesel engines.
2. Related Art
It is known that diesel engines consume relatively high amounts of oil, and in the process, produce undesirable exhaust emissions. As such, continual efforts exist to both improve diesel engine oil consumption performance, which in turn, results in improved exhaust emissions. Unfortunately, due to the materials commonly used for diesel engine cylinder liners, such as cast iron and steel, and the cylinder bore finishing processes required, such as honing, to attain high performance standards for the engine, there is little progress being made with respect to the liner to improve oil consumption and to reduce exhaust emissions.
With this, there is one known design feature that can be used on the liner side to improve oil consumption, and in turn, reduce exhaust emissions. The feature goes by several names, including “saver rings”, “anti-polishing rings”, “fire rings”, “anti-scuffer rings”, and “scraper rings”. Regardless of its name, the feature is an annular band made of suitable material that is inserted into an annular recess machined in the top of the cylinder liner. The annular band has an inner diameter providing an overhanging portion that is slightly less in diameter than the inner diameter of the cylinder liner, with the overhanging portion taking up most of the crevice volume, wherein the crevice volume is defined by an inner wall of the cylinder liner, a piston top ring and piston top land.
As such, the overhanging portion of the annular band acts to clean the top land of the piston as the piston approaches a top-dead-center position (TDC) by scraping deposits from the land, sometimes referred to as bore polishing. In addition, the overhanging portion of the band acts as a mechanical barrier to upward scraped oil and oil throw-off, both of which are major contributors to oil consumption. As such, the band provides beneficial results in that it reduces oil consumption, reduces exhaust emissions, and also prolongs the useful life of the engine.
Although the annular bands described above are beneficial to the performance of the engine and to the environment, they come at a cost. As explained, the bands are constructed as separate rings of material, and thus, not only due the bands require separate manufacturing operations from the cylinder liner, but also require the cylinder liner to have secondary machining operations for their installation. In addition, given the nature of their use, the tolerances between the band and the cylinder liner need to be closely controlled to ensure proper performance of the engine. Accordingly, manufacturing and assembly efficiencies are diminished through the incorporation of the bands, and thus, the cost to produce engines utilizing the bands is increased.
A cylinder liner manufactured according to the present invention overcomes or greatly minimizes any limitations of the prior art described above, thereby allowing diesel engines to operate at an increased performance level, while reducing their oil consumption and exhaust emissions, and improving their useful life, all at a reduced overall cost.